An important weakness has been discovered in the technology of quantum key distribution (QKD), which is increasingly being used by military and government to secure sensitive communications.
Researchers at the University of Toronto have successfully attacked a QKD system from Swiss company, id Quantique, the first time an attack on a commercial system using the technology has been demonstrated.

The highly-theoretical attack was based on disproving assumptions about the levels of errors which can be taken by either the sender (Alice) or receiver (Bob) to be indicative that the key data has been compromised by a third party (Eve).

The security principle of QKD is the impossibility of a simple intercept-and-resend attack being hidden from sender or receiving parties, normally taken to a quantum bit error rate (QBER) of 20 percent or greater becoming apparent in the signal, a figure that takes account of a degree of 'noise'.